SE541687C2

SE541687C2 - A method and an apparatus for analyzing the condition of an electric drive system

Info

Publication number: SE541687C2
Application number: SE1751376A
Authority: SE
Inventors: Samer Shisha
Original assignee: Scania Cv Ab
Priority date: 2017-11-07
Filing date: 2017-11-07
Publication date: 2019-11-26
Also published as: WO2019093943A1; SE1751376A1

Abstract

An electric drive system (1) comprises an electric machine (3), an assembly (4) for supplying electric energy to the machine when this operates as motor and store electric energy when the machine operates as generator, and a converter (7) having an AC-side (9) connected by an electrical energy feeding line (10) to the machine and a DC-side (6) connected by an electrical energy feeding line (8) to the assembly (4). The condition of the electric drive system is analysed by measuring the voltage on at least one location along one of said feeding lines during operation of the electric drive system so as to then evaluate the voltage signal so obtained by obtaining the content thereof and comparing this with the content of reference voltage signals. Faults of the electric drive system may then be predicted or detected.

Description

A method and an apparatus for analyzing the condition of an electric drive system TECHNINCAL FIELD OF THE INVENTION The present invention relates to a method for analyzing the condition of an electric drive system, said system comprising an electric machine configured to, when operating as motor, drive a shaft on an object, an assembly configured to supply electric energy to said machine when this operates as motor and store electric energy when said machine operates as generator, and a converter having an AC-side connected by an electrical energy feeding line to said machine and a DC-side connected by an electrical energy feeding line to said assembly, as well as an apparatus for carrying out such a method according to the preamble of the appended independent apparatus claim.

The invention relates to methods for analyzing the condition of electric drive systems for any type of use, such as industrial applications, in grinding machines and all types of motor vehicles, although the invention is particularly applicable to motor vehicles and especially wheeled utility vehicles, such as trucks or lorries and buses. This is the reason for mainly discussing the invention for this particular use without for that sake restricting it thereto. Thus, said object is in such a case a motor vehicle, which is then a hybrid vehicle driven by an internal combustion engine besides by said electric machine or a purely electric vehicle.

In the case of an electric drive system in a motor vehicle the energy storage/source in said assembly is typically electric batteries arranged in the vehicle, but it may also comprise a pantograph on the vehicle taking electric energy from an electric power line in motor operation of the electric machine and feeding electric energy into the power line when the electric machine operates as generator when braking the vehicle.

BACKGROUND ART In common to all electric drive systems is the importance of detecting faults therein as early as possible and preferably be able to predict the occurrence thereof so that downtimes of the objects driven thereby may be avoided or in any case kept as short as possible. Such downtimes are particularly disadvantageous for an electric drive system in a motor vehicle, in which the electric drive system is used for the propulsion of the vehicle and also as main generator to charge the batteries to be used for all the electric components in the vehicle. A consequence of this is that field quality issues related to the electric drive system will naturally lead to the vehicle being inoperable, i.e. costly vehicle off-road (VOR) problems.

US 2015/0154816 A1 discloses a system for monitoring the status of a vehicle by detecting the voltage output by the vehicle’s battery when the vehicle’s engine is turned on and off and voltage output by the converter while the engine is running. The operation of the status of the vehicle’s battery and inverter is determined from such voltage measurements.

However, there is of course an ongoing attempt to provide a method and apparatus for analyzing the condition of an electric drive system being improved with respect to known such methods and apparatuses.

SUMMARY OF THE INVENTION The object of the present invention is to provide a method and an apparatus of the type defined in the introduction being improved in at least some aspect with respect to such methods and apparatuses already known.

This object is with respect to the method obtained by providing such a method with the features listed in the characterizing part of appended patent claim 1.

Thus, by in a step a) measuring the voltage on at least one location along at least one of the feeding lines between the assembly and the electric machine during operation of the electric drive system, in a step b) evaluating the voltage signals obtained by said measuring by obtaining the content thereof and comparing this with content of at least one reference voltage signal and in a step c) determining whether a fault exists or the occurrence of a fault is approaching in the electric drive system on basis of said evaluation, existing faults may be detected early or even predicted before occurring. The content of the voltage signal, which may be obtained by for instance using Fourier transform analysis, may then be compared with the content of reference voltage signals in the form of healthy drive system reference voltage content first and foremost and/or content of possible signals from possible failure modes of the electric drive system, so that the fault and/or predicted failure may be determined and in the motor vehicle case be communicated to the driver and/or a workshop for the vehicle. The method may then also be used to predict faults in the electric drive system before they occur as the signal analysis can detect changes in the signal that can indicate that a certain fault might be imminent. Thus, an electric drive system maintenance can be planned and done before the actual fault occurs.

According to an embodiment of the invention said voltage measuring is carried out on a said at least one location close to or at the connection of a said electrical energy feeding line to said converter. The occurrence of noise in the voltage signal measured disturbing the evaluation thereof is minimized by measuring the voltage on a said location close to or at the connection to the converter, in which it is particularly preferable but not necessary, to carry out the measurement on the AC-side of the converter, since there is a risk that other electric equipment may disturb the voltage signal on the DC-side of the converter slightly. Another option is to measure the voltage close to the electric machine or even at the electric machine. However, according to another embodiment of the invention the voltage measuring is carried out on the electric feeding lines on both sides of the converter, which increases the reliability of the measurement result and the possibility of detecting and/predicting faults even more.

According to another embodiment of the invention at least step a) is performed at determined time intervals, such as in the case of an electric drive system in the motor vehicle, each time the vehicle is driven or for instance once each driving hour, since the method will be carried out automatically and without in any way disturbing the function of the electric drive system, the operation of the vehicle or the driver of the vehicle.

According to another embodiment of the invention the method is carried out on an electric drive system of an object in the form of a vehicle being a hybrid vehicle driven by an internal combustion engine besides by said electric machine or a purely electric vehicle. As mentioned above, a method according to the invention is particularly advantageous for the application on an electric drive system of a motor vehicle.

According to another embodiment of the invention the voltage signal data obtained by performing at least step a) is stored in storage means in an electric system of the vehicle and/or wirelessly sent to a member remotely located, such as in a workshop for the vehicle. By storing the voltage signal data this may be processed and considered in a workshop, such as when the vehicle visits a workshop for maintenance thereof. Although it is advantageous to perform the evaluation and determining steps of the method directly in the vehicle when driving the vehicle these steps may also be performed in a said workshop when visited by the vehicle or before or after such visiting. The collected reference voltage content may be stored in the remote member, and the reference list of unhealthy voltage contents and their actual fault relations as detected by workshops and/or analysis engineers may thus be stored/analyzed and the database content increased continuously as new failure modes and related unhealthy signal contents detected in a continuously learning system.

According to another embodiment of the invention an action drawing the attention of the driver of the vehicle to the fact that it is determined that a fault exists or a fault is approaching is carried out. This makes it possible for the driver to take the measure judged to be most appropriate in relation to the information delivered, such as directly driving to the closest workshop or taking care of the issue at a later moment.

The object of the present invention is with respect to the apparatus for analyzing the condition of an electric drive system obtained by providing an apparatus for analyzing the condition of an electric drive system, said system comprising an electric machine configured to, when operating as motor, drive a shaft on an object, an assembly configured to supply electric energy to said machine when this operates as motor and store electric energy when said machine operates as generator, and a converter having an AC-side connected by an electrical energy feeding line to said machine and a DC-side connected by an electrical energy feeding line to said assembly, in which the apparatus comprises an arrangement configured to measure the voltage on at least one location along at least one of said feeding lines between said assembly and the electric machine during operation of the electric drive system, and a device configured to evaluate the voltage signal obtained by the measuring by said arrangement by obtaining and analyzing the content thereof and comparing this with content of at least one reference voltage signal and to determine whether a fault exists or the occurrence of a fault is approaching in the electric drive system on basis of said evaluation.

The advantages of such an apparatus and embodiments thereof defined in the dependent apparatus claims appear clearly from the above discussion of a method according to the invention and embodiments thereof.

According to an embodiment of such an apparatus this comprises or is configured to transmit data to a storage and processing system remotely located with respect to said electric drive system and configured to be continuously updated and learning from said faults previously detected and reference voltage content relating thereto. This means in the case of an object in the form of a vehicle that this storage and processing system will be updated and increased by continuously obtaining data from vehicles and their known fault modes, i.e. the way the voltage signal typically looks like in connection with occurrence of a particular fault in the electric system, once these fault modes have been identified and linked to the related signal content.

The invention also relates to a computer program, a computer program product, an electronic control unit and a motor vehicle according to the appended claims directed thereto.

Other advantageous features as well as advantages of the present invention appear from the description following below.

BRIEF DESCRIPTION OF THE DRAWINGS With reference to the appended drawings, below follows a specific description of embodiments of the invention cited as examples.

In the drawings: Fig. 1 illustrates very schematically an electric drive system having an apparatus for analyzing the condition thereof and to which a method according to the invention is applicable, Fig. 2 is a flow chart illustrating the steps performed by a method according to an embodiment of the invention, and Fig. 3 is a schematic view illustrating an electronic control unit for implementing a method according to the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION Fig. 1 illustrates very schematically an electric drive system 1 arranged in a motor vehicle 2 and having an electric machine 3 for propulsion of the vehicle when operating as motor. The electric drive system has also an assembly, in the form of electric batteries or other electric energy storage devices 4, configured to supply electric energy to the electric machine when this operates as motor and receive and store electric energy from the machine when this operates as a generator, such as when braking the vehicle or when the vehicle is driven by an internal combustion engine 5 of the vehicle, when this is a hybrid vehicle.

The electric batteries are connected to a DC-side 6 of a converter 7 through an electrical energy feeding line 8. The AC-side 9 of the converter is connected through an electrical energy feeding line 10 to the electric machine. Accordingly, the converter operates as an inverter when electric energy is fed from the electric batteries to the electric machine and as a rectifier when electric energy is fed in the opposite direction. The operation of the converter 7 is controlled by an electronic control unit 11 of the electric system of the vehicle participating also in the control of other electric equipment on board the vehicle.

A number of faults may occur in the electric drive system 1 of this type, such as shortcircuits in stator windings of the electric machine, ruptures in said windings, rotor issues as loosening of permanent magnets thereof, start of bearing seizing and malfunction of power electronic components in the converter for mentioning some examples of such faults. Such faults may influence the voltage on both sides 6, 9 of the converter, mostly already when an occurrence thereof is approaching. An apparatus for analyzing the condition of the electric system according to the invention does for that sake have an arrangement 12 configured to measure the voltage on both sides of the converter 7, here at the very connections 13, 14 of the respective electrical energy feeding line 8, 10 to the converter. Voltage signals so obtained are sent to a device 15, which may be separate or included in the electronic control unit 11 , configured to evaluate the voltage signals so obtained by obtaining the content thereof, such as by using Fourier transform analysis. Excessive or abnormal harmonic content in the alternating voltage on the AC-side 9 of the converter and abnormal noise in the direct voltage on the DC-side 6 of the converter may then for instance be detected. Such noise in the direct voltage may indicate that the rectifier function of the converter does not work properly. Preanalyzing of different possible fault modes and investigating what happens to voltage signals just before the faults occur may have been carried out and data so obtained may then have been stored in the electronic control unit 11 for being accessed by the device 15 as a reference precursor. The reference data can also be stored remotely and called by the electronic control unit 11 when required/observed necessary. Thus, such reference signals or their indicators are then inserted into the electronic control unit, and the device 15 is then able to compare said content of the voltage signals obtained through said measurements with the possible signals associated with the possible failure modes and thus determine the fault and/or predicted failure directly and communicate this to the driver and/or wirelessly to a workshop 16. The results of the voltage measurements carried out by the arrangement may also be stored by storing means 17 in the control unit 11. Results of the evaluation and comparison carried out by the device 15 may also be stored in the storage means 17. Data so stored may be investigated and considered when the vehicle visits a workshop, for instance for maintenance purposes.

Fig. 2 illustrates a flow chart of the method according to an embodiment of the present invention carried out for an electric drive system in a vehicle. The method is started with the steps Si of measuring voltage on the output on the AC-side of the converter. A Fourier transform analysis of the voltage signal so obtained is then carried out in a step S2. Voltage signal content obtained by said analysis is then in a step S3 compared with the content of reference voltage signals. In subsequent step S4 the result of the comparison in the step S3 is used to determine existence of fault or approaching occurrence of fault in the electric drive system.

Computer program code for implementing a method according to the invention is with advantage included in a computer program which can be read into an internal memory of a computer, e.g. an internal memory of an electronic control unit of a motor vehicle. Such a computer program is with advantage provided via a computer program product comprising a data storage medium which can be read by a computer and which has the computer program stored on it. Said data storage medium is for example an optical data storage medium in the form of a CD ROM disc, a DVD disc etc., a magnetic data storage medium in the form of a hard disc, a diskette, a cassette tape etc., or a flash memory or a memory of the ROM, PROM, EPROM or EEPROM type. Fig. 3 illustrates very schematically an electronic control unit 11 comprising an execution means 18, e.g. a central processor unit (CPU), for execution of computer software. The execution means 18 communicates with a memory 19, e.g. of the RAM type, via a data bus 20. The control unit 11 comprises also a non-transitory data storage medium 21 , e.g. in the form of a flash memory or a memory of the ROM, PROM, EPROM or EEPROM type. The execution means 18 communicates with the data storage medium 21 via the data bus 20. A computer program comprising computer program code for implementing a method according to the invention, e.g. in accordance with the embodiment illustrated in Fig. 2 is stored on the data storage medium 21.

The invention is of course in no way restricted to the embodiments described above, since many possibilities for modifications thereof are likely to be obvious to one skilled in the art without having to derivate from the scope of invention defined in the appended claims.

Another option than starting the voltage measuring and analysis at determined time intervals is to trigger the analysis by predetermined signals or manual request by a computer or human interaction.

Claims

1. A method for analyzing the condition of an electric drive system (1 ), said system comprising an electric machine (3) configured to, when operating as motor, drive a shaft on an object (2), an assembly (4) configured to supply electric energy to said machine (3) when this operates as motor and store electric energy when said machine operates as generator, and a converter (7) having an AC-side (9) connected by an electrical energy feeding line( 10) to said machine (3) and a DC-side (6) connected by an electrical energy feeding line (8) to said assembly (4), characterized in that the method comprises the steps of: a) measuring the voltage on at least one location (13, 14) along at least one of said feeding lines (8, 10) between said assembly (4) and the electric machine (3) during operation of the electric drive system, b) evaluating the voltage signal obtained by said measuring by obtaining the content thereof and comparing this with content of at least one reference voltage signal, and c) determining whether a fault exists or the occurrence of a fault is approaching in the electric drive system on basis of said evaluation, and d) before step a) carrying out preanalyzing of different possible fault modes, and investigating what happens to voltage signals from said at least one location just before the faults occur, storing data so obtained and using these data as reference voltage signals in step b).

2. A method according to claim 1 , characterized in that said voltage measuring is carried out on a said at least one location (13, 14) close to or at the connection of a said electrical energy feeding line (8, 10) to said converter (7).

3. A method according to claim 1 or 2, characterized in that said voltage measuring is carried out on the electrical energy feeding lines (8, 10) on both sides (6, 9) of the converter (7).

4. A method according to any of the preceding claims, characterized in that at least step a) is performed at determined time intervals.

5. A method according to any of the preceding claims, characterized in that the method is carried out on an electric drive system (1 ) of an object in the form of a vehicle (2) being a hybrid vehicle driven by an internal combustion engine (5) besides by said electric machine (3) or a purely electric vehicle.

6. A method according to claims 4 and 5, characterized in that at least the step a) is carried out each time the vehicle (2) is driven.

7. A method according to claims 5 or 6, characterized in that the voltage signal data obtained by performing at least step a) is stored in storage means (17) in an electric system of the vehicle and/or wirelessly sent to a member (16) remotely located, such as in a workshop for the vehicle.

8. A method according to claim 7, characterized in that the steps b) and c) are performed in a workshop (16) visited by the vehicle, such as for maintenance thereof.

9. A method according to any of claims 5-7, characterized in that when in step c) it is determined that a fault exists or a fault is approaching an action drawing the attention of the driver of the vehicle to this fact is carried out.

10. An apparatus for analyzing the condition of an electric drive system (1 ), said system comprising an electric (3) machine configured to, when operating as motor, drive a shaft on an object (2), an assembly (4) configured to supply electric energy to said machine (3) when this operates as motor and store electric energy when said machine operates as generator, and a converter (7) having an AC-side (9) connected by an electrical energy feeding line (10) to said machine (3) and a DC-side (6) connected by an electrical energy feeding line (8) to said assembly (4), characterized in that the apparatus comprises • an arrangement (12) configured to measure the voltage on at least one location (13, 14) along at least one of said feeding lines (8, 10) between said assembly (4) and the electric machine (3) during operation of the electric drive system (1 ), and a device (15) configured to evaluate the voltage signal obtained by the measuring by said arrangement by obtaining and analyzing the content thereof and comparing this with content of at least one reference voltage signal obtained by prior preanalyzing of different possible fault modes and investigating what happens to voltage signals from said at least one location just before the faults occur and storing data so obtained and to determine whether a fault exists or the occurrence of a fault is approaching in the electric drive system (1 ) on basis of said evaluation.

11. An apparatus according to claim 10, characterized in that said arrangement (12) is configured to carry out said voltage measuring on at least one location (13, 14) close to or at the connection of a said electrical energy feeding line (8, 10) to said converter.

12. An apparatus according to claim 10 or 11 , characterized in that said arrangement (12) is configured to perform said voltage measuring on the electric energy feeding lines (8, 10) on both sides (6, 9) of the converter.

13. An apparatus according to any of claims 10-12, characterized in that said arrangement (12) is configured to be arranged in a motor vehicle (2) being a hybrid vehicle driven by an internal combustion engine (5) besides by said electric machine (3) or a purely electric vehicle and to carry out said voltage measuring on an electric drive system (1 ) of that vehicle.

14. An apparatus according to claim 13, characterized in that it further comprises means (17) configured to receive and store voltage signal data obtained through the voltage measuring of said arrangement for later evaluation, such as in a workshop (16) to be visited by the vehicle.

15. An apparatus according to any of claims 10-14, characterized in that the apparatus comprises or is configured to transmit data to a storage and processing system (16) remotely located with respect to said electric drive system (1 ) and configured to be continuously updated and learning from said faults previously detected and reference voltage content relating thereto.

16. A computer program comprising computer program code for causing a computer to implement a method according to any of claims 1-9 when the computer program is executed in the computer.

17. A computer program product comprising a non-transitory data storage medium which can be read by a computer and on which the program code of a computer program according to claim 16 is stored.

18. An electronic control unit (11 ) of a motor vehicle comprising an execution means (18), a memory (19) connected to the execution means and a non-transitory data storage medium (21 ) which is connected to the execution means (18) and on which the computer program code of a computer program according to claim 16 is stored.

19. A motor vehicle, especially a wheeled vehicle such as a truck or a bus, characterized in that it comprises an apparatus according to any of claims 10-15 and/or an electronic control unit (11 ) according to claim 18.